Somatosensory Evoked Potential (SEP) tests have been employed for at least twenty years to monitor spinal cord function during surgical procedures. Surgical instrumentation or procedures may produce stress on the spinal cord. Repeated measurement of somatosensory evoked potentials during surgery provides electrophysiological data that may be used by the surgical team to make diagnostic decisions regarding global spinal cord function and nerve root trauma.
Nevertheless, somatosensory evoked potentials are not specific to individual nerve roots because they employ peripheral nerves that comprise nerve fibers that enter the spinal cord through several adjacent nerve roots. Consequently, somatosensory evoked potential wave forms are often not sufficiently specific to identify pathologies associated with individual nerve roots.
A Dermatomal Somatosensory Evoked Potential (DSEP) is produced by placing a stimulating surface electrode in a dermatomal field, such as an approved dermatome site, and recording the signature electrical response from scalp electrodes positioned on the head of a patient over the patient's somatosensory cortex. The evoked response to this peripheral stimulus theoretically can be used to evaluate the sensory input through individual sensory nerve roots.
Dermatomal somatosensory evoked potentials have been successfully employed to monitor spinal cord function during spinal surgery and to document successful spinal root decompression. Unlike somatosensory evoked potentials, the evoked response measured by the dermatomal somatosensory evoked potentials can be used to evaluate the sensory input through individual sensory nerve roots.
Patients with radicular pain often elect to pursue a conservative course of therapy that may initially include a combination of physical therapy and spinal manipulation. Such therapy may include the use of equipment such as the ACTIVATOR, or other similar equipment. Because the sensory components of nerve roots, especially the dorsal root ganglion, may be anatomically more vulnerable to mechanical or chemical pathology, patients may exhibit radicular pain and/or sensory loss without significant motor involvement. Although physical therapy and spinal manipulation may sometimes relieve these effects, no methods currently exist that may be used to correlate the resolution of problems with the performance of physical therapy using objective measurements.